System of motor control.



P ATENIBD. BBQ'. 1o, 1907. w; L. MERRILL-51;@ SYSTEM 0F MOTOR CONTROL-L' APPLICATION FILED APB..6.1907.

'To alluiohomit may concern:

UNITED sTATEs PATENT OFFICE.

-WILBUR L. MERRILL, OF SGHENECTADY, NEW YORK, ASSIGNOR COMPAYY, A CORPORATION OF NEW YORK.Y

To GENERAL ELECTRIC SYSTEM OF MOTOR CONTROL.

" 'citizenofi-tithe; United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful vImprovements in. Systems of Motor i Control, of which the following is a specification.

. 'p cms'in which a i ployed'to drivea loadat diiierent speeds,

".'Myinvention relates to the control of elecmotors, and particularly to control sysplurality of motors are em- `v`fIn certain cases, as, for instance, in the operation of turrets on battleships and of printing-presses', which must be .operated over a wide range of speed, it has been pro- 4'lposed heretofore to employ two motors one of which is of small capacity and is connected l 'i to.l the load through low-speed gearing, while "theother'inotor is larger and is connected to the motor through high-speed gearing. By

` impressing aj low voltage K on the smaller or low-speed'motor, and gradually increasing it,

'fand then i pressing a low voltage on the high-speed motor and gradually increasing it,

' a v'the load ymay be driven over 'a wide range of convenient method of securing the variablevoltage for operating the motors, consists in varying the field strength of the generaftors supplying the motors, but with control`devices heretofore employed, this method ";of"si`1pplying the'inotors has a serious disadvantagefs'ince, when the'transition is made from low-speed to the high-speed motor, the

*impressed voltage must` be reduced from rushofculrent and shock maximum to minimum, in order to prevent a to'the apparatus,

lbut the iield-.strength-o the generator does impressed on the high-speed motor when it is ii'rst thrown 'into circuit'. This will produce an excessive rush of current and a sud- 'den 'acceleration of the load.

My invention consists in providing means l for `preventing a sudden movement of the controlling switch in changing from one mo- 1 tor to another; I accomplish this by pro- Vviding ya magnet connected in shunt to the -'ger`1erator,"and consequently responsive tovariations in the generator voltage, and a Specification of Letters Patent.

Application filed April 6. 1907. Serial No. 366|79 vvent this,

Patented Dec. 10, 1907.

lock controlled by the magnet arranged to engage the controlling switch when tiren-- switch is moved to change from one motor to the other. The lock is released automatically when the voltage ofthe generator falls low enough so .that the generator mav bev connected to the high-speed motor without an undue rush of'current. l The controlling-switch contacts are preferably so arranged that in the position in which the switch is locked the low-speed motor is disconnected fromthe load, while the high-- speed motor has its circuit still open. Consequently, if the switch were left in this position, the load would come to rest. To pre- I provide means controlled by the locking magnet for connecting the high-speed .motor to the generator, independently of the controlling switch, as soon as the generator voltage falls low enough to permit of suc connection without anv eXces'sive'current iiow. My invention will best be understood by reference vto the accompanying drawing, which shows diagrammatically a control system arranged in accordance with my invention. In the drawing A represents a drivenmember, which is shown as a gear engaging a ,pinion on a shaft which carries two motor armatures B B. These motors coperate tot' drive the load at high-speed.

C re resents the armature of asmall motor, w ich is connected to the shaft of the motors through a pinion 'and gear and a magnetic clutch D. T efields b b of the large motors and the eld c ofthe small motor may be supplied directly fromthe constant potential mains E. The armatures are supplied from the armature F 'of anelectric generator, which may be driven at a constant speed by the shunt motorG connected to the' constant potential mains E. The i'eldf of this generator is connected to the mains through a controlling switch H, which comprises a resistance I, by which the ield strength of the generator may be varied so as to control the voltage suplplied to the f motors.. The controlling switc comprises stationary contacts h1 to hm. The .movable portion of the switch carries, in addition to the movable contacts, plates J J, each of which has a downwardlyextending lug ada ted to be engaged by anupwardly extending stem on the core-'of a magnet K- when the magnet is energized. The core oi magnet K is provided with a contact which controls'the magnets L L, which are arranged to connect the motor armatures B B tothe generator inde endently of the controlling switch H.

This circuit may be traced as follows :--froml the upper main E to contact hg, contact k12, resistance I, field f, thence through contacts huand h1", to the lower main E. All of the resistance I is included in circuit with the field winding, so that the generator voltage is low. The .motor C starts and drives the load at a low s eed, since the circuit of the magnetic' clutc D is closed. This `circuit may be traced from the lower line-wire E, through the magnetic clutch, and contacts hl and h", to .the up er main-E; As the movement ofthe switc H is continued, resistance Iis gradually' short-circuited by contacts 71,15, h, h, and hf, thereby increasing the voltage impressed on the armature C, and consequently increasing its speed. lVhen the resistance I is all short circuited, the motor is operating at its maximum speed. Ii' the movement of the controlling switch H is continued beyond this point, the circuit of the `magnetic clutch D is opened at conteft'h?,

and the short circuit around resistance I is o ened at contact h. At the same instant, t e downwardly-extending lug on the plate J engages and is `stopped by the upwardly projecting stem 'on t e core of magnet K, since the core has been raised by the magnet,

' as the generator voltage, which is now at its maximum value is impressed on the terminals of .the magnet. Although resistance I is again cut into the field circuit of thel generator,

' mediately fall, so that if the movement of the switch H'were continued, so as to connect the generator to the motors B B, a heavy frush of current would follow, but the energization of magnet K prevents the continued movement of the swift-ch. until the generatorvoltage has 'fallen suiiiciently to cause magn net K to` drop its core; thereby releasing switch H, and allowing 'the movement of the switch to be continued. A further move-l ment of the switch closes a circuit from inoj generator is now 60.

tors B B to generator F, through contacts h, h, h5 and h. The minimumfi'iroltage of the impressed on motors B B. The gearing between motor C' and motors B B is so designed. that the speed of motors B o eri@v 'ig on minimum voltage ispractically t e san. asthat-offmotor C on maximum voltage .196

V'ltiplied -by the gear ratio, `so that thetrans;v @from motor C to motors Bis "contact ofmag'net K, to contacts ha the generator voltage does not im-' accomplished without a shock to gradually Further movement of switch H short circuits resistance I, thereby gradually increasing the speed of motors B upto their maximum value.- The armaturecircuit of 70 the motor C may be left closed, so that the motor runs idle, or may be broken at contacts ha and h4 after the lug on plate J has passed the stem of magnet K. On the reverse movement of switch H the' speed of the load is gradually decreased.

It will be seen that since at the point Where the switch H is locked by the core of magnet K the circuit of clutch D has been broken, while the circuit of motors B B has not been closed, the load is not being driven by' either the low` speed or high speed motor. lConsequently, it the switch were left in the position at which it is locked, the load would c. slow down. In orderto prevent this, I profi vide the magnets L L, which are controlled by a contact on the core of magnet K. As soon as the generator voltage falls suffi-l cientl to cause magnet K to drop its core, the circuit of the magnets L L is closed. `This circuit may be traced as follows: from the lower mains E, through the magnets L L and and-7L9 and'thence to `upper main E. These magnets L L are consequentlyv energized and close their contacts as soon as magnet Kreleases its sore; thereby connecting-armatures B B directiy to the generator independently of the switch H. Consequently, even if the movement of switch H is not continued after its release by themagnet K, motors-B B will be connected to the generator as soon as the voltage of the generator falls-sufiicientlyto permit the connection.' Whenever the movement of switch H. is .continued and the'circuit of motor armatures B B closed through contacts h5 and h, the circuit of magnets LL is broken at contact hs'. i

The left hand movable contacts of switch H are arranged like the right hand contacts,

except that the connection of generatoriield 'f to the mains is reversed, so as to reverse the'.

hdirection of rotation of the motors.l

What I claim as new and desire to secure by Letters Patent of the United States, is,

Ti. In combination with a load to be driven, an electric motor for driving the load at low speed, a second electric motor, for driving the load at high speed, a common sourceof current for the motors, controlling means adap'ti20 ed to connect the first motor to the source and gradually to increase the voltage of the source and then to lower the voltage ofthe smirce andv connect the second motor thereto, and means for reventing a'sudden operation 125 of said contro ing means in changing `from one lfnotor to the other.

2. In combination with a load to be driven,

lan electric motor for driving the load at low load at high speed, a common source of current for the motors, controlling means adapted to connect the irst motor to the source and gradually to increase the voltage of the source and then to lower the voltage of the source and connect thesecond motor thereto,

and means controlled by the voltage of thesource controlling the operationof said controlling means in changing from one iiotor to the other.

3. In combination with a load to be driven, an. electric motor for driving the load at low speed, a second electric motor for driving the load at high speed, a common'source of cur.

rent for the motors, controlling means adapt-l ed to connect the irst motor to the source and gradually toin'crease the voltage of the source and then to lower the voltage of the source and connect the -secondmotor thereto, and a magnet connected in shunt to said source controlling the operation of said controlling means in changing from one'motor to the other.

' thereto, a magnet connected in shunt to said source, and a lock controlled by said magnet y adapted to engage said switch when said switch is moved to change from one motor to the other.

'5, In combinationwith a load 4to be driven, an electric motor for driving the load at low speed, a second electric motor for driving the load at high speed, a common source of current for the motors, controlling means adapted to connect the first .motor to the source and gradually to increase the voltage of the source and then to lower the voltage of the source and connect the second motor thereto, a device adapted to prevent a sudden operation of said controlling means in changing from one motor to theother, and means controlled by said devicev for connecting the second motor to the4 source independently of said controlling means.

6. In combination with aload to be driven,

an electric motor for driving the load at low speed, a second electric motor for driving the load at high-speed, a common source of current for the. motors, a controlling switch adapted to connect the first motor to the source and gradually increase the-voltage of the source andthen to ,lower the-voltage of the source and connect the second motor thereto, a magnet connected in shunt to said sourcev controlling' the movement of` said 'switch in changing'from one motor to the other, and contacts controlled by' said magnet for connecting the second'motor to the source independently ofsaid switch.

7. In combination withia load to be driven,

an electricmotor for driving the load at low speed, a second electric motor for driving the load at high speed, a common source`- otcurrent for the motors, a controlling lswitch adapted to connect the first motor to the source and gradually to increase the voltage of the source and then to lowerthe voltage of the source and connect the second motor the source controlling the movement of said switch in changing vfrom one motor to the other, and contacts controlled by said'device for connecting the second motor .to the source independently of said switch.

8. In combination with a load tobe driven, an electric motor for driving the load at lowv speed, a second electric motor for driving the load at high speed, a common source of current for thel motors, a controlling switch adapted to connect 4the first motor to the source and gradually to increase the voltage of the source and then to lower the voltage of the source and connect the second motor thereto, a deviceadapted to preventl a sud den movement of said switch in changing from one motor to the other, and contactsv` A source and gradually to increase the voltage of the source and then to lower the voltage -tov the source and connect the second motor thereto, a magnet connected in shunt to said source, a lock controlled by saidmagnet adaptedl to engage said switch when said switch is moved to change from one motor to the other, and contacts controlled by the voltage of the source for connecting the sec- 'ond motor. tothe source independently of said switch.

10. In combination with a load to b e driven, an electric motor for driving the load at low speed, a second electric motor for driv.- ingthe load at high speed, a generator for supplying current to said motors, controlling meansadapted to connect the first motor to the generator and gradually to strengthen the eld of the generator and then to weaken said field and to connect thesecond motor to the generator, and means for preventing a sudden operation of said controlling means in changing from one motor to the other.

. 11. In combination with a load to be driven, an electric motor for driving the load v at low speed, asecond electric motor for drivingltheload at high speed, a generator for supplying current to said motors, acontroln llng switch`to connect the rst'inotor to the ene'rator and gradually to strengthen the' eld of the vgenerator-and then to weaken -xflsaid'fl'eld and to connect the second motor to "thejgenerator magnet connected in shunt tothe enerator armature, and a lockcontrolled y said Inagnet adapted to 'engage said switch 'when said switch is moved to bange from one motor to the other.

i 12. In combination with a load to be tor. to the generator and gradually strengthen the field of the vgenerator and then to weaken said ield andl to connect the second motor to the generator, means for ree venting a sudden movement of said sWitc in changing from one motor to the other, and contacts controlled by the generator voltage for connecting the second motor to the generator independently of said switch.

In witness whereof7 I have hereunto set" my hand '5th day otApril, 1907.

I WILBUR L, MERRILL.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD. 

